Prior art patents include: U.S. Pat. No. 4,042,777; U.S. Pat. No. 4,381,502; U.S. Pat. No. 4,502,038; U.S. Pat. No. 4,555,193; U.S. Pat. No. 5,267,181; U.S. Pat. No. 654,291; U.S. Pat. No. 4,655,621; U.S. Pat. No. 5,642,108; U.S. Pat. No. 5,649,223A; WO9315454A1; WO9315454A1; and WO1993015454A1.
Embodiments of this invention are for a one-handed, chording keyboard.
Chording keyboards have been in use for decades as special purpose keyboards, for example, by stenographers, court reporters, braille entry, and by people with handicaps. Prior chording keyboards have not been successful at replacing QWERTY keyboards for general use.
Because chords are multiple keys pressed at one time, some method of “disambiguating” chords is required, since it is not possible to press the exact chord key combination for all keys perfectly simultaneously.
The most common method for disambiguation is to require that all keys be released between chords. The recognized chord is then the key combination with the most keys pressed between the all-released states. The disadvantage of this method is that multiple actions are required for each chord—specifically multiple finger presses and multiple finger releases, for most (>50%) chords.
Another disambiguation method in the prior art (e.g. U.S. Pat. No. 40,427,777) is to use a single key release, or a first key release as a trigger to recognize the chord. This method has the serious problem that the user-performed transitions between chords change depending on the chord pairs. Chording is hard enough to learn without the now hundreds of different chord transitions to learn for this method.
Some prior art chording keyboards permit a single finger to press more than one key at a time. This approach is fundamentally different than a “pure” chording keyboard in which each finger presses only key at a time; it may permit one-handed operation due to the larger number of available keys. However, precise finger positions are required, and thus learning time is long and the mistake rate is relatively high.
Some prior art disambiguation algorithms are aimed at telephone-style keyboards being used for text, where each key may represent more than one letter. These approaches generally required a dictionary to guess what word the user is attempting to type. These keyboards are also not pure chording keyboards, where there is a high correspondence (75% to 100%) between a single chord and a single letter or function.
Some prior art use time for disambiguation. The idea is that the time interval required by the user between one key and another key to achieve all keys pressed for a chord (“cord creation gaps”) is less than the time that all chord keys are held down. The serious problem with this method is: first, that the chord creation gap time is highly variable by the individual user, the user's experience, how tired or distracted the user is, and the complexity of the source text. Thus, the selection of a maximum time threshold for allowance of cord creation gaps must either be variable, or long. Variable timing produces highly inconsistent keyboard operation, which is highly unpredictable and undesirable for users. The second problem with this method is that it limits the maximum typing rate. Since users often choose to learn and use a chording keyboard in order to increase their typing speed over a QWERTY keyboard, this limitation defeats the primary reason to use such a keyboard.
Non-patent literature includes:
GKOS (“Global Keyboard Open Standard”) shown on the web URL, gkos.com, downloaded 6 Mar. 2014.
A challenge with chording keyboards is that the user is not able to depress multiple keys with multiple fingers truly simultaneously. Thus, for some transition period of time, the input is ambiguous. Two solutions exist in the prior art to resolve such ambiguity. The first solution requires that chords be held for a minimum period of time, a chord resolving (or disambiguation) time. The second solution requires that all keys be released between combinations, then to select the key combination where the most keys were simultaneously depressed as the chord.
The problem with the first solution is that, in practice, it does not work reliably. More advanced users need a shorter resolving time so that the keyboard keeps up with their typing speed. Beginning users need a longer resolving time to avoid accidentally encoding extra characters. However, a more serious problem is that the ambiguity time varies significantly by which keys are in the chord and the by sequencing of chords, with some sequences being more difficult, and therefore take longer to resolve. In addition, users are not consistent. For example, a user that is tired is likely to require longer resolving times. Thus, neither fixed nor selectable resolving times are an effective means of resolving chord ambiguity.
The problem with the second prior-art solution is that two sets of finger motions are required to encode each symbol. That is, fingers must first depress the keys in each chord, then release those keys. While the requirement to both depress and release for each symbol is also a requirement for common QWERTY keyboards, QWERTY keyboards require only a single finger action for each key, which, in aggregate, is less finger motion and less hand muscle activity to enter symbols than for a chording keyboard in this prior art implementation. In addition, in a QWERTY keyboard potential ambiguity due to multiple keys being depressed at the same time is normally resolved by simply using only the depressing of a key to indicate desired action of that key, and then ignoring the hold time or release time of keys.
Since a key purpose of chording keyboards is efficiency—as measured by either typing speed, or the convenience of using only hand for typing, the efficiency loss as described above, when compared to QWERTY keyboards, is the primary reason that chording keyboards are not widely used.